incremental zfs backup

delete_old_snapshots.sh

#!/bin/sh

export PATH=/usr/local/sbin:/sbin:/usr/local/bin:/bin:/usr/sbin:/usr/bin

#DEBUG="echo"
DEBUG=""

set -eu # -x

TODAY=$(date +%Y-%m-%d)
NOW=$(date +%s)
KEEP_DAYS=30

HOST=backup.server.example.com
SSH_PORT=22
RUSER=remote_username
SSH_KEY=/path/to/ssh_key
SSH="ssh -p $SSH_PORT -i $SSH_KEY $RUSER@$HOST"

#ping -c 3 ${HOST} || exit 1

FS=zroot/testfs
RFS=zroot/backups/testfs

## check if remote fs is mounted
yesno=$($SSH zfs get -Hp mounted ${RFS} | awk '{print $3}')
if [ "$yesno" != "yes" ];then
    exit 2
fi

LOCAL_GUID="$(zfs get -Hp -o value guid ${FS}@backup)"
for SNAP in $($SSH zfs list -Hp -o name -t snapshot $RFS); do
 GUID="$($SSH zfs get -Hp -o value guid $SNAP)"
 if [ "$GUID" == "$LOCAL_GUID" ]; then
  echo skip $SNAP
  continue
 else
  CREATION="$($SSH zfs get -Hp -o value creation $SNAP)"
  if [ $((NOW - CREATION)) -gt $((KEEP_DAYS*86400)) ]; then
    echo Deleting $SNAP
    $DEBUG $SSH zfs destroy $SNAP
  else
    $DEBUG echo Keeping $SNAP
  fi
 fi
done

zfs_backup.sh

#!/bin/sh

export PATH=/usr/local/sbin:/sbin:/usr/local/bin:/bin:/usr/sbin:/usr/bin

set -eu  -x

TODAY=$(date +%Y-%m-%d)

HOST=backup.server.example.com
SSH_PORT=22
RUSER=remote_username
SSH_KEY=/path/to/ssh_key
SSH="ssh -p $SSH_PORT -i $SSH_KEY $RUSER@$HOST"

# do not run if last snapshot is today
LAST_SNAP_TIME=$(zfs get -Hp -o value creation $FS@backup)
LAST_SNAP_DATE=$(date +%Y-%m-%d --date=@$LAST_SNAP_TIME)
[[ $LAST_SNAP_DATE == $TODAY ]] && exit 1

#ping -c 3 ${HOST} || exit 1

FS=zroot/testfs
RFS=zroot/backups/testfs

## check if remote fs is mounted
yesno=$($SSH zfs get -Hp mounted ${RFS} | awk '{print $3}')
if [ "$yesno" != "yes" ];then
    exit 2
fi

## snap and send diff
zfs snapshot ${FS}@${TODAY}
zfs send -i ${FS}@backup ${FS}@${TODAY} | $SSH zfs recv -F ${RFS}
## rotate
zfs destroy ${FS}@backup
zfs rename ${FS}@${TODAY} ${FS}@backup